Sure. I use conditioned tap water. Hard water with a 7.6 ph. I kept my tank at 84 but it's currently at 82. The higher temp will make the discus eat more but will also allow oxygen to leave the water quicker and cause food to spoil sooner. As for filtration. Buy a test kit and keep an eye on it. It will vary greatly depending on how much and how often you feed. I have a 300 GPH canister filter that is more than adequate yet doesn't quite suffice spending how how I'm feeding. I recently took a gamble and put a colony of 10 wild caught hypancistrus in the bottom of my discus tank which increased my bioload.... But since I over fed already not much changed because just cleaned up what my discus didn't get to quick enough